There are changes in periodontal tissues during puberty, pregnancy and after menopause in human females. During pregnancy, for example, chronic inflammatory diseases are often aggravated and there are changes in mineral metabolism that might affect osseous tissues, including bone, dentin and cartilage. The problems associated with changes in osseous tissues in the absence of gonadal function (e.g. post-menopausal osteopenias) are well recognized. The proposed experiments will continue to investigate changes in periodontal tissues during reproduction and in the absence of ovarian function. The following objectives will be studied during pregnancy and lactation in rats: 1) To determine the effect of dietary calcium on calciotrophic hormones (vitamin D, parathyroid hormone) and the resultant changes in calcium metabolism and osseous tissues (bone, cartilage and dentin). Biochemical and morphometric approaches will be used. 2) To determine if changes in mineralized tissues in early pregnancy require factors from the placenta. For this experiment the changes that occur in pseudopregnancy will be characterized. 3) To determine the role of the placenta in mediation of the changes in mineral and skeletal metabolism at mid-pregnancy. Particular emphasis will be placed on defining the role of placental lactogens. 4) To define the role of the somatomedin/insulin-like growth factor system on periodontal tissues during pregnancy. For this experiment immunoreactive and bioactive somatomedin-like substances will be studied. 5) To determine the changes in the proliferative capacity of the periodontal ligament during pregnancy and lactation. The relative proliferation of fibroblasts in the unstimulated and mechanically stimulated PDL will be determined. 6) To determine the changes in periodontal tissues in the absence of ovarian function, following ovariectomy. These studies should yield important new information on changes in female periodontal tissues (osseous and soft tissues) during different life cycles influenced by the presence or absence of reproductive hormones. These studies will also provide information relevant to aggravated inflammatory states of the oral cavity, endocrine osteopenias, and post-menopausal osteoporoses.